We have a Keysight 34970A connected to a host PC with an Adlink PCIe interface card. I have tried communicating with the logger from my own program, Command Expert and also from the GPIB Interactive control in the Adlink GPIB utility
.
In each case the logger will not accept the DISPlay:Text command if I supply it with a string (e.g. 
ISPlay:TEXT "test"). I get the error back from the 34970A "SCPI Error: 550,Not able to execute command in local mode", however the command DISPlay:TEXT:CLEar is always accepted.
Previously I had the logger connected using the Adlink USB3488A SUB-GPIB adapter and did not experience this problem.
According to the manual, error 550 means the instrument has received a READ? command while in local mode for RS232 operation.
I have tried tried pressing the local button on the front panel, sending SYSTem:LOCal (gives the error "SCPI Error: 514,RS-232 only: not able to execute using GPIB"), and factory resetting the logger. None of these make any difference.
Does anyone have any ideas as to resolve this problem? I am quite new to SCPI and GPIB and feel like I might be missing something obvious